foo.cc: In function 'int main()':
foo.cc:14:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |  while (i<s.length())
      |         ~^~~~~~~~~~~
foo.cc:17:11: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |   while (j<t1.length())
      |          ~^~~~~~~~~~~~

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